There is presently no cure for multiple sclerosis (MS). Currently available immunomodulatory therapies do not modify the pathogenesis of axonal degeneration once it is established and are only partially effective in preventing permanent disability accumulation in MS patients. Identifying a drug that stimulates endogenous myelination and thereby prevents axon degeneration could theoretically halt disease progression. To this end we have recently discovered that treatment with an estrogen receptor (ER) 2 ligand diarylpropionitrile (DPN) can induce functional endogenous remyelination in experimental autoimmune encephalomyelitis (EAE). This is the first pharmacological agent that has been shown to activate remyelination and to reverse axon damage in the presence of inflammation. Treatment with the ER2 ligands would likely be very well tolerated in males and females as both reproductive behavior in females as well as breast and uterine endometrial cancer are mediated through ER1, not ER2. Guided by recently published and preliminary data we would like to make the transition from bench (treatment of EAE) to bedside (treatment of MS). The goal of these studies is to determine the viability, pharmacokinetics and toxicity of ER2 ligands (DPN-Tocris and SAR143953-Sanofi Aventis) required by the FDA to move the compounds forward into testing in humans and in the clinic. The goals of this study are: to determine the lowest dose of ER2 ligands that can effectively stimulate endogenous myelination and restore functional axon conduction; to assess the critical window of time during disease during which ER2 ligands can restore demyelinated and neurodegenerative axons in a mouse model of MS; and to conduct conventional toxicity studies in rat to determine the safety of the compound. The results obtained from the study will complete the preliminary steps in the pipeline for pre-clinical development necessary to begin clinical testing of treating with ER2 ligands to prevent demyelination and axon injury in the nervous system.